A seemingly mild-mannered Travis Frederick articulated one of those differences after his first practice with the Cowboys.

“The thing I like about football the most is that you get to do things on the field you can’t do off the field,” Frederick said. “It would be pretty illegal just to beat you up, but on the field I get a chance to do that. I get a chance to legally beat somebody up.

“I take advantage of that when I can.”

What the legal system views as a misdemeanor — or worse — is perfectly acceptable in the NFL, particularly among offensive linemen. This attitude is one of the reasons the Cowboys used a first-round pick on the center from Wisconsin.

This Jekyll-Hyde disorder is no character flaw. It’s a quality the Cowboys desperately need in the interior of the offensive line, which explains why the club was compelled to reach for Frederick near the end of the first round.

Frederick crossed the 200-pound threshold in fifth grade. A few years later, as a 16-year-old junior in high school, he crushed the scales at 300 pounds for the first time.

At this point, some would succumb to a cheap Big Foot joke, but it’s no joke. Frederick attended Big Foot High School in Walworth, Wis.

He now stands 6-3 and weighs 317 pounds, so prod at your own risk. Frederick certainly fits the prototype of offensive coordinator Bill Callahan, who favors centers who resemble a tree stump with arms.

“We like that big guy in the middle,” Callahan said, stressing the first word of his response. “We all do.

“At 320, there is a lot of size and range that eats up that middle. You’re capable of setting in the hole, setting in the middle and providing more of a swell in there.”

Now, about that Frederick temper…

It was an issue in middle school where it would flare up on and off the field. Baseball was Frederick’s sport of choice then. He denies ever purposely throwing at an opponent, but he did hit a few batters.

“I wasn’t the best pitcher as far as accuracy,” Frederick said.

The anger subsided the older Frederick became. He didn’t even use it on the football field.

The coaches at Wisconsin helped pull that aggression out of him so he could use it to his advantage. So did John Moffitt, the player Frederick replaced at left guard for the Badgers before moving to center.

Moffitt has started 16 games at guard for the Seattle Seahawks over the last two seasons.

“He took me under wing, taught me how to flip that switch and since then I’ve been able to do it,” Frederick said.

Much has been made of the fact that the 5.56 the rookie ran at the NFL scouting combine is the slowest time in the 40 by any center drafted in the last 20 years.

Not enough has been made of the 34 that Frederick scored on the Wonderlic test. Quick recognition is more important for a center than foot speed.

“Especially at center, you have to be able to direct everybody,” Frederick said. “The speed of the game is much faster, the tempo of getting to the ball and calling the cadence. You have to be able to recognize that stuff a little faster. And hopefully be able to make all of the calls for everyone else as well.”

Frederick will get that chance. Cowboys owner Jerry Jones expects the rookie to come in and contribute immediately as a starter.

“There is competition, but there certainly ought to be a spot for him in that offensive line,” Jones said. “He has the combination of skill and mental to be able to come in and play immediately.”

Frederick makes no assumptions.

“I don’t believe anyone on the starting line right now is saying, ‘Oh, they drafted this guy, he should be the guy,’’’ Frederick said. “It’s not going to be that way.

“I’m going to have to fight for it. I’m going to have to prove I’m the best guy for it.”

The first step in that quest was taken Friday.

“He’s a smart guy,” Garrett said. “He’s certainly played a lot of football in his life, and he has great command at the center position, but he’s a long way off. He’s got a lot to learn.

“He, like all of the rest of the rookies, has a long way to go.”

Follow David Moore on Twitter at @DavidMooreDMN

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Travis Frederick is one of five offensive linemen — and only the second center — ever taken in the first round by the Cowboys.